APHY 201 Osmosis and Diffusion LAB

In beaker 1, the solution on the right side of the membrane currently has a higher osmotic pressure than the solution on the left side of the membrane

False

In beaker 2, the solution on the right side of the membrane could eventually have the same concentration of particles as the solution on the left side of the membrane

False

In beaker 2, the solution on the right side of the membrane has a higher osmolarity than the solution on the left side of the membrane

False

In beaker 2, the solution on the right side of the membrane has a higher osmolarity than the solution on the left side of the membrane and will gain water from the solution on the left side of the membrane

False

In beaker 1, the solution on the right side of the membrane has a (higher or lower) osmolarity than the solution on the left side of the membrane

Right side lower osmolarity

1. Describe the relationship between the change in mass of the dialysis bags and the concentrations of sucrose inside the bags.

The percent change in mass increases as the initial concentration of sucrose increases inside the bags.

Do the results support the predictions you made before beginning the experiment?

The results for temperature and concentration support the predictions made from Fick's Law of Diffusion, but not molecular weight. The heavier congo red actually diffuses faster and further through the agar, because congo red is more soluble in the agar than methylene blue. This observation does NOT make Fick's Law incorrect, instead incomplete. Solubility is not part of the original Fick's Law of diffusion.

1. What would be different in your results if the membranes were permeable to the solute particles?

The sucrose would reach equilibrium across the membrane decreasing the net diffusion of water into the bag lowering the mass of each bag.

. In beaker 1, the solution on the right side of the membrane could eventually have the same osmolarity as the solution on the left side of the membrane

True

. In beaker 2, the solution on the right side of the membrane has a lower osmotic pressure than the solution on the left side of the membrane

True

. In beaker 2, the solution on the right side of the membrane will lose water to the solution on the left side of the membrane

True

In beaker 1, the solution on the right side of the membrane could eventually have the same concentration of solute particles as the solution on the left side of the membrane

True

In beaker 1, the solution on the right side of the membrane is currently losing water

True

Do you think incubating the agar plates at different temperatures will affect the diffusion rate? If so, how?

Yes. According to Fick's Law of Diffusion, the warmer temperature should cause the dyes to diffuse faster and further through the agar compared to the colder temperature.

Increasing molecular weight _______________

decreases diffusion rate

ISOTONIC

0.9% (eg. NaCl) Cell volume remains same No osmosis

HYPOTONIC

< 0.9% Cells swell (hemolysis) Osmosis into cell

HYPERTONIC

> 0.9% Cells shrink (crenate) Osmosis out of cell

How did concentration (FS or 50%) have an effect?

According to Fick's Law of Diffusion, concentration directly effects the rate of diffusion.

What effect does molecular weight have on diffusion rate through agar?

According to Fick's Law of Diffusion, molecular weight inversely effects the rate of diffusion.

How did temperature effect the pattern of diffusion?

According to Fick's Law of Diffusion, temperature directly effects the rate of diffusion.

Make a prediction about the rates of diffusion of methylene blue and Congo red dye through the agar gel. Congo Red 697 daltons Methylene Blue 320 daltons

According to Fick's Law of Diffusion, the lower molecular weight methylene blue should diffuse faster than the heavier molecular weight congo red.

1. Predict what would happen in an experiment if all the bags were placed in a 0.4M sucrose solution instead of water.

Bag B would decrease in mass, Bag C no change in mass, and Bags D, E, and F would increase in mass, but not as much as placed in a beaker of water.